Oregon 21-604 FlexiBlade 68-Feet Donut of String Trimmer Line 0.158-Inch Gauge Leaves a cleaner cut in grass Cuts through dense weeds and berry vines More cutting power than traditional trimmer line Quieter than trimmer line and safer than steel weed blades The .099" and .105" diameters can be used in most manual-feed trimmer heads. FlexiBlade is not recommended for most "bump feed" trimmers